Volume 21, Issue 9, Pages R338-R345 (May 2011) The Molecular Mechanism and Evolution of the GA–GID1–DELLA Signaling Module in Plants  Tai-ping Sun  Current Biology  Volume 21, Issue 9, Pages R338-R345 (May 2011) DOI: 10.1016/j.cub.2011.02.036 Copyright © 2011 Elsevier Ltd Terms and Conditions

Figure 1 GA biosynthesis and deactivation pathways in plants. (A) Bioactive GAs in seed plants. GA3 is the most abundant active GA made in fungi. GA4 is the major active GA in Arabidopsis. The common features of active GAs are highlighted in red in GA4. (B) GA9 methylester and several other GA methylesters (not shown) are antheridiogens in ferns. (C) GA biosynthesis pathway from GGDP, and GA deactivation by GA2ox. The solid arrow indicates a single-step reaction. The unfilled arrow indicates a multiple-step reaction. GGDP, geranylgeranyl diphosphate; CDP, ent-copalyl diphosphate; CPS, ent-copalyl diphosphate synthase; KS, ent-kaurene synthase; KO, ent-kaurene oxidase; KAO, ent-kaurenoic acid oxidase; GA13ox, GA 13-oxidase; GA20ox, GA 20-oxidase; GA3ox, GA 3-oxidase; GA2ox, GA 2-oxidase. The active GAs are labeled in red, GA biosynthesis enzymes are labeled in purple, and the deactivation enzyme is labeled in orange. Current Biology 2011 21, R338-R345DOI: (10.1016/j.cub.2011.02.036) Copyright © 2011 Elsevier Ltd Terms and Conditions

Figure 2 The GA–GID1–DELLA complex. (A,B) Crystal structure of the complex that contains GA3, AtGID1A and the DELLA domain of GAI (an AtDELLA). (A) The molecular surface of the complex. (B) Ribbon representation. The carboxy-terminal GID1 core domain is labeled in blue, the GID1 amino-terminal extension (N-Ex) is in cyan, and the DELLA domain is in pink. The bound GA3 is represented as a space-filling model with carbon in green and oxygen in red. (C) A model for the GA-dependent GID1–DELLA interaction and subsequent SCFSLY1 binding. GA binding first induces a conformational change in the N-Ex of GID1 for DELLA binding, which promotes binding of the GRAS domain of the DELLA protein to GID1. This stable complex enables efficient SCFSLY1 recognition and subsequent degradation of DELLA by the proteasome. This figure was modified from Murase et al. [35]. Current Biology 2011 21, R338-R345DOI: (10.1016/j.cub.2011.02.036) Copyright © 2011 Elsevier Ltd Terms and Conditions

Figure 3 The interaction network between the GA–GID1–DELLA signaling module and other internal and external cues. The GA–GID1–DELLA regulatory module is highlighted in orange. Signals that promote bioactive GA accumulation are labeled in blue, whereas signals that reduce GA levels are highlighted in purple. DELLA interacts directly with multiple regulatory proteins (PIFs, SCL3, ALC and JAZs; highlighted in green) to mediate crosstalk between GA and other signaling pathways (light and JA signaling, and root and fruit patterning). Activation or inhibition could be via different modes of action: PD, protein degradation; PPI, protein–protein interaction; TC, transcription. SAM, shoot apical meristem; ABA, abscisic acid; JA, jasmonic acid. Current Biology 2011 21, R338-R345DOI: (10.1016/j.cub.2011.02.036) Copyright © 2011 Elsevier Ltd Terms and Conditions